This invention relates to diagnostic instruments and in particular provides an instrument for testing or assessing dermatomes in peripheral neurological examinations.
A dermatome is an area of skin delimited in extent by the supply of sensory fibres from a single spinal nerve. A diagnostic or investigative analysis of dermatomes can therefore reveal to the skilled medical practitioner information relating to certain aspects of the condition of the patient's spinal cord.
According to the present invention a dermatome testing instrument comprises a barrel member and a probe member, in which the probe member is slidable longitudinally relative to and preferably within the barrel member and is resiliently biased towards a position in which the tip region of the probe member extends from the barrel member.
The tip of the probe member is preferably formed to a rounded point which is fine enough to permit of precise application to particular skin areas or dermatomes without being so sharp as to cause undue discomfort to the patient.
In use, the barrel member is held in the hand of the medical practitioner and the tip of the probe member is tapped gently and repeatedly against the patient's skin, and the response or reaction of the patient is taken into account by the practitioner in arriving at an opinion or diagnosis. The resilience of the probe member has the effect of cushioning the tapping, whereby the force exerted by the instrument, or the sensation experienced by the patient, is primarily a function of the strength of the resilient biassing of the probe member and only secondarily, within reasonable limits, of the power exerted by the medical practitioner. The tapping force on the patient's skin is therefore rendered more consistent, and diagnosis rendered more precise, than with non-resilient testing instruments.
Optionally, the probe member may be fully retractable within the barrel member, for transport or storage without damage being caused to or by the tip. Conveniently, the instrument is similar in size to a pen, whereby it may be carried in the pocket, and may be formed with or include a clip and/or a removable cap which may itself include a tongue extending longitudinally from the skirt edge thereof and which forms a clip in conjunction with the external surface of the barrel member.
Preferably the barrel member and probe member are formed from metallic materials and the barrel member in particular may be of any desired shape or formed with any pattern or ornamental features for functional or aesthetic purposes.